[Nobbie]

I'm just knocking down an old outhouse and there is lots of old crumbly mortar available. I've sieved it and will use the bigger bits for my paths, but I was wondering if the fine stuff would help improve my heavy clay soil? I think I've heard of gypsom being used and suspect this is similar to the old mortar I have.

Any advice on this?

[JayG]

Hard to say - on the one hand mortar does contain sand, lime and probably a little gypsum, which could help, on the other hand one of the components of cement is clay! 

That's the chemistry - no experimentation done here on my sandy soil ; perhaps someone else has actually tried it...

[mumofstig]

The allotments here are where some poor quality housing was demolished, many years ago; the brickdust and mortar (there are still pockets of the stuff found) do nothing to help the clay soil. Personally I'd avoid adding it, better to add organic matter of any kind to improve the soil.

[Tenhens]

Hard to say - on the one hand mortar does contain sand, lime and probably a little gypsum, which could help, on the other hand one of the components of cement is clay! 

That's the chemistry - no experimentation done here on my sandy soil ; perhaps someone else has actually tried it...

The amount of gypsum in cement is approximately 3-5%  and is used to control the setting time. Many years ago I was able to source ground gypsum to help break down some tough soil , from what I recall it didn't make that much difference.

Clay has been used in the production of cement , in wet process, where it gets burnt at high temperature - 1000 C Plus ,  Due to the high cost of 'wet' process ,it has as far as I'm aware  become redundant in the UK

I would agree with Mumofstig and  add   organic matter.  May take a bit of time but looking long term will benefit the plants ,which once they have served their purpose can be added to the compost and then added to the soil

[Goosegirl]

Using gypsum and lime can break up clay particles but it can take a long time to show any results. Best thing is to use any organic matter and mix in some coarse sand and grit which will also help with drainage.

[Growster...]

I thought lime made the clay more crumbly, and therefore lighter?

May be wrong, but I'd chuck the lot in as well a lot of compost/manure, and stand well back..;0)

The capilliary action will do wonders for getting nutrients down to the roots!

[upert]

I read somewhere - any gardening book will probably feature it - that you add organic material to break up clay. A lot of it. I was part of a group that improved an awful clay plot by adding dozens of wheelbarrows of leaves and woodchip. The soil is now much better for it - unfortunately we later found honey fungus nearby and that feeds on dead wood but has yet to migrate to that plot.

I'd not add mortar, I'd still go with whatever is organic, free and nearby.

[Plot 1 Problems]

Another advocating organic amendment. My clay has improved beyond all recognition in three years by adding as much compost and municiple compost as I could get my hands on. I haven't dug it in particularly deeply, just mulch each autumn with a fresh layer, lightly forked or hoed into the top of the soil just before planting out.

[sunshineband]

Another advocating organic amendment. My clay has improved beyond all recognition in three years by adding as much compost and municiple compost as I could get my hands on. I haven't dug it in particularly deeply, just mulch each autumn with a fresh layer, lightly forked or hoed into the top of the soil just before planting out.

I can agree with this approach through personal experience, and feel it would be the best way forward with any clay soil that needs lightening